In Lovàsz's seminal work [1]},
he gives an injective semi-ring homomorphism of the “Burnside semi-ring”
of the categoryThere seems no decisive name of
this classical construction of semi-ring, e.g., appearing in the
construction of Burnside rings. The definition is given
shortly after as \({{\operatorname{Dec}}}({\mathcal {C}},+,\times )\) .
of finite directed graphs (and more generally, of finite relational structures)
to an infinite product of the copies of the semi-ring \({\mathbb {N}}\) .
